Trails/MTB guides in the Aveyron?

Perhaps you have been there, and felt the Mistral whistling past as you descend the sweetest forest trails you've ever ridden. Or, grumpily read STW online before trudging round a castle with your family, bikeless and bereft.

If it's the former, where did you do it, and where might a man hire a bike and or guide to help him do the same?